Die for rolling screw-threads



(No Model.)

2 811 t Sh t 1 H. K.JONES. DIE FOR ROLLING SCREW THREADS. v

- No. 502,258. Patentgd July 25, 1893.

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(N 0 Model.)

I H. K. JO DIE FOR ROLLING 80 witnesses.

THREADS. Patented July 25, 189-3.

' IvwomTon 2 Sheets- Sheet 2.

UNITED STATES PATENT OFFICE.

HORACE K. JONES, OF HARTFORD, ASSIGNOR TO THE RUSSELL & ERWIN MANUFACTURING COMPANY, OF NEW BRITAIN, CONNECTICUT.

DIE FOR ROLLING SCREW-THREADS.

SPECIFICATION forming part of Letters Patent No. 502,258, dated July 25, 1893.

Original application filed May 24, 1892, Serial No. 434,152. Divided and this application filed February 27. 1893. Serial No.

463.821. (No model. I

To all whom it may concern.-

Be it known that I, HORACE K. JONES, acitizen of the United States, residing at Hartford, in the county of Hartford and State of Connecticut, have invented certain new and useful Improvements in Dies for Rolling Screw- Threads, of which the followingis a specification.

My invention relates to improvements in dies for rolling screw threads, and the chief object of my improvement is to produce a superior die having all or part of the several features hereinafter described.

In the accompanying drawings, Figure 1 is a plan or face view of one member of a pair of dies made in accordance with my invention. Fig. 2 is an enlarged transverse section of the same on the line w :r of Fig. 1. Fig. 3 is a like section on the liney y of Fig. 1. Fig.

4 is another like section on theline z z of Fig.

1. Fig. 5 is a diagram illustrating the manner of cutting my die grooves. Fig. 6 is a plan view of a die block having three grooves cut therein, representing the grooves, of my die 2 5 in a somewhat exaggerated form. Fig. 7 isa longitudinal section of the same through the center of one of said grooves. Fig. Sis a plan View of another form of my die, somewhat exaggerated for the purpose of better illustration. Fig. 9 is a longitudinal section of a portion of the same through the center of one of its grooves. Fig. 10 is a transverse section of the same on the line 1: 1;. Fig. 11 is a transverse section of the same on the line 83. Fig.

12 is an end view of my die block with a modi-.

fied form of grooves, and Fig. 13 is an enlarged diagram illustrating the form of such die grooves at various points along their length.

I form my die groove by means of a wabbling cutter arranged to rotate on a spindle in connection with suitable mechanism, so that the cutter may run perfectly true at one point and from that point gradually change 5 its angle of inclination and wabble more as it passes through the die grooves thereby forming a tapering groove and one whose shape in transverse section varies gradually throughout its whole length. My application,

Serial No. 434,152, filed Flay 24, 1892, and of which this specification is a division, shows and describes my apparatus for milling these die grooves.

In order to disclose how my die may be made and also for a better understanding of the form of the grooves,lherein show the diagram, Fig. 5, which illustrates the cutter at having beveled edges specially designed for milling die grooves, said cutter being so controlled by special mechanism that it runs perfectly true at one point of itstraverse through each groove of the die block as indicated by the broken contour lines in the middle of the groove in the block b at which point a perfect V shaped groove will be formed; while as the die block advances, the angleof inclination or wabbling movement is gradually and constantly increased to bring the cutter into the positions represented by the full and broken lines in said diagram and a groove is made in the form of a truncated V with sloping sides and a curved bottom as shown in the sectional view of the block b in said Fig. 5, the change in form between said two points in the groove being gradual throughout the entire length thereof. It will also be observed that if the wabbling movement should be still greater, the cutter would run out at the face of the block b and the curved bottom would constitute the entire cross section of the groove as indicated by the curved bottom in Fig. 5 in connection with the continuation thereof on each side in broken lines. This diagram represents a cutter which is round in side view and mounted concentrically on the axis 0. The diametrical line on which the cutter rocks in changing its angle of inclination, I term the Wabbling axis and it extends at right angles to the spindle axis, the two axes crossing each other at d, and this point of crossing repre- 9o sents the center of the circle on whose arc the curved bottom of the groove is formed. If, however, the cutter should be somewhat oval, or eccentrically mounted on the axis 0, the curved bottom of the groove in cross section will be on a sharper curve. In all cases the parts of the grooves which have a right line in cross section are formed by the beveled sides of the cutter while the curved portions are given their form by the points of the teeth :00

or edge of the cutter. The die grooves 15 in Figs. 1, 2, 3, 4, 6, 7, 8, and 9 are of the form thus explained in connection with the diagram, Fig. 5, and each have the curved bottom 16 and sloping side walls 17 which gradually merge into or form a true V shape at what .1 term the focusing point where the cutter runs true. This point is at w m in Fig. 1, at the upper end of the die block in Fig. 6, the right hand end of the block in Fig. 7, at s s in Fig. 8, and in the middle of the diagram Fig. 13. As in ordinary dies for rolling screw threads, the grooves extend along the length of the die block somewhat obliquely, the angle of inclination being determined by the position in which the die block is set with reference to its movement across the axis of the cutter in being milled. For convenience I will describe each groove as if they all extended alike from end to end of the die block, although in fact some of them are shorter by extending across the corners of the block.

The die block, Figs. 1 to 4 (which is one of a pair of dies) is provided with the ordinary raised portion lat for rolling the thread on the point of the screw and this ordinary feature may be used in connection with any of the dies herein illustrated if desired. The grooves on this raised portion are of the same general form as on the rest of the die. A special mechanism may be employed to enable the cutter to pass over and mill this portion in the same manner as it traverses and mills the flat portion of the die blocks. Inasmuch as the grooves 15 taper and gradually widen from the focusing point at or near the finishing end of the die toward the opposite and entering end, it is obvious that the fiat tops of the ridges between said grooves taper in the reverse direction. The ridges at the entering end of the die, Fig. 1, are fiat on the top as the adjacent grooves do not run together, but in some cases I prefer sharp ridges at the entering end of the die as hereinafter described. Vhile the grooves gradually widen from the focusing point a: a: in Fig. l to the entering or lower end of the diein said figure they also widen in like manner from said focusing point toward the upper end of the die, but the taper is so slight and the distance so short that it is impossible to properly represent the same in such a drawing.

In order to more clearly illustrate my die I have shown other figures in which the features that I wish to claim are magnified or exaggerated in order to more clearly illustrate them. In Fig. 6 I have illustrated a die block with three grooves in which the focusing point is at the upper end of the block where the grooves are a true V shape. The grooves have the same general form, that is to say a curved bottom and sloping sides with a gradually warped surface, but I have represented the grooves so wide at or near the entering end (which is the lower end in Fig. 6) that they run together and form a ridge with a sharp edge at the point it a and from that point these sharp ridges slope gradually to the end of the die as best shown at 18, in Fig. 7. I also make these grooves slightly diverging at the finishing end (the upperend in Fig 6) and this I accomplish by moving the die block after each traverse of the cutter, not only the proper distance for cutting another groove, but so as to change its angle of inclination slightly and make the grooves farther apart at the finishing end. This (11- vergence is exaggerated in Figs. 6 and 8, because the actual divergence in a die for a medium sized screw is only about three one thousandths of an inch. The die block, Fig. 8, has the same general form of grooves, but instead of being milled with a round cutter, they were milled with acutterthat was slightly oval, whereby the curve at the bottom of the groove is made sharper. In this die the line .9 8 represents the focusing point and theline o v the point where the flat tops of the ridges between the die grooves vanish and from which the ridges continue in the form of sharp ridges which slope toward the end of the die block as at 19, Fig. 9. In the sloping portion at the entering end of the die block, Figs. 6 and 7, the ridges have sloping side walls which form a rightline in cross section, but in the die, Fig. 8, the sloping side walls vanish at the point e 'v as shown by the transverse section, Fig. 10, and from that point on to the end of the block the sharp ridges are formed wholly by the meeting of curved surfaces. When a cutter that is V shape in edge view and oval in side view is used whose eccentricity exceeds the depth of the grooves in the die block, the tapering portion of the groove will be in the form of a modified V, or a V with curved sides as shown in Figs. 12 and 13 and a true V shape at the focusing point as shown at the middle point of the diagram 13. The curved lines on each side of this middle V represent sections through the tapering portions of the grooves at several successive points along the length of the grooves from which it will be seen that the sides of the grooves of this form as well as in the form first described have a warped surface extending along their length with a constantly changing angle of inclination.

A die having the sloping sides of its grooves in cross section curved in the form of a modified V as shown in Fig. 12 and illustrated by the diagram, Fig. 13, I have made the subject of another application, Serial No. 434,151, filed May 24., 1892.

By making the grooves gradually widening at the finishing end of the die, I am enabled to form a more perfect thread as the pressure on the thread is slightly relieved before the screw leaves the die blocks so that it is less liable to be indented in its discharge therefrom while at the same time a good finish is given to the thread. This feature Iconsider an improved form of the finishing end of the die in my patent of April 8, 1.890, in which the grooves are made parallel for a short dis- IIO tance at the finishing end of the die. In this same patent I also specify grooves in the form of a truncated V for a portion of their length with rounded grooves having narrow ridges at the entering end of the die. The curved grooves and narrow ridges at the entering end of the die herein shown have the same functions and objects as in said patent. The beveled sides of the groovesin my new die are believed to have a better action by the gradual change of their angle of inclination from end to end, that angle being less at the wider part of the groove. By making the ridges come to an edge and slope toward the entering end of the die, the dies take hold of the stock by sharp ridges with a shallow penetration and then work in deeper until the point a u or c Q), is reached and from that onward, the penetration may be continuous or changing according to the position in which the faces of the dies are set relatively to each other. By making the grooves diverge slightly toward the finishing end, I pro vide for the gradual enlargement of the circumference at the top of the thread as it is built up above the core so that when the thread in rolling leaves one groove (as for instance at the edge of the die) to engage the next one it will strike the middle of said groove, instead of one side and squarely enter the same and consequently pass squarely through the dies in a direction parallel to the point threading portion instead of traveling in the arc of a circle. The divergence should be only just enough to accommodate the rise of the stock or the increased diameter as the thread is rolled, whereby the screw is made to travel squarely over the face of the die and parallel to the point threading portion. The distance that the blank travels in making one revolution is constantly increased as the threads are built up, for the inclined sides of the threads bearing on the walls of the grooves effects the rolling action of the blank. I call the distance that the blank travels in making one revolution the rolling circumference of the thread. This circumference is between the top of the thread and its core and I make the divergence in the grooves such that the distance from one groove to the next in the longitudinal direction of the die is as nearly as possible equal to the rolling circumference of the thread as rolled by that portion of the die and thus the distance from one groove to the next gradually increases toward the finishing end in proportion to the increased distance that the blank will travel at each revolution as the thread is built up. By thus giving the die grooves the proper amount of divergence as above described, I accomplish in another way the same object that I accomplished by the die patented to me January 13, 1891, No. 444,554, in which the point threading portion was on the arc of a circle and consequently parallel to the path of the screw through the dies.

I am aware that a prior patent shows and describes dies for rolling screw threads in which the grooves diverge toward the finishing end to such an extent as to take up the excess of metal by an elongation of the screw instead of an enlargement or building up of the thread beyond the normal diameter of the stock, and I hereby disclaim the same. In my die the divergence does not prevent the natural increase of diameter and is only just snflicient to make the screw travel squarely through the dies.

It will of course be evident thatthe construction of any portion of my die as herein shown and described will not be changed by merely omitting certain portions from either or both ends of the die block, for example, if the die block, Fig. 8, were cut off on the line 8 s and on the portion remaining would be precisely the same as that now shown and described, and it would form an operative die.

I claim as my invention 1. A die for rolling screws, having its face provided with alternate tapering ridges and grooves,.the latter varying in transverse section from a V shape at or near the finishing end to the form of a truncated V with a curved bottom at or near the entering end, said ridges being fiat on their tops for the main portion of their lengths, substantially as described and for the purpose specified.

2. A die for rolling screws having its face provided with alternate tapering ridges and grooves, the sides of the latter having a warped surface extending along their length with a constantly'changing angle of inclination, substantially as described and for the purpose specified.

3. A die for rolling screw threads having on its face alternate tapering ridges and grooves, the latter having curved bottoms at the entering end of the die with their sides running together while the ridges between them at the points so run together are brought to an edge and slope toward said entering end, substantially as described and forthe purpose specified.

4. A die for rolling screw threads having on its face alternating tapering ridges and grooves, and a finishing portion in which the grooves taper in the reverse direction from that of the rest of the die, substantially as described and for the purpose specified.

5. A die for rolling screw threads, having inclined ribs that diverge toward the finishing end substantially in proportion to the progressively increasing diameter of the thread, the distance between the ribs on a line parallel with the line of the ridge of the point forming part of the die being at any part of the die practically equal to the rolling circumference of the thread as rolled at said part, substantially as described and for the purpose specified.

IIORAOE K. JONES. Witnesses:

T. S. BIsHoP, M. S. WIARD. 

